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United States Patent |
5,655,282
|
Hodek
,   et al.
|
August 12, 1997
|
Low thermal conducting spacer assembly for an insulating glazing unit
and method of making same
Abstract
An insulating unit has a pair of glass sheets about an edge assembly to
provide a compartment between the sheets. The edge assembly has a U-shaped
spacer made of metal, metal coated plastic, gas and moisture impervious
polymer, or gas and moisture impervious film coated polymer. The outer
legs of the spacer and the glass provide a long diffusion path to limit
the diffusion of argon gas out of the compartment. The edge assembly has
materials selected and sized to provide edge assembly having an RES-value
of at least 75. A spacer for use in insulating units includes a plastic
core having a gas impervious film e.g. a metal film or a halogenated
polymer film. Also taught herein are techniques for making the unit and
spacer.
Inventors:
|
Hodek; Robert Barton (Gibsonia, PA);
Kerr; Thomas Patrick (Pittsburgh, PA);
Misera; Stephen C. (Tarentum, PA);
Siskos; William Randolph (Salem Township, PA);
Thompson, Jr.; Albert Edward (Allegheny Township, PA)
|
Assignee:
|
PPG Industries, Inc. (Pittsburgh, PA)
|
Appl. No.:
|
412028 |
Filed:
|
March 28, 1995 |
Current U.S. Class: |
29/469.5; 29/527.4; 29/897.312; 52/786.13; 72/379.2; 156/107; 156/109 |
Intern'l Class: |
B21D 035/00; E06B 003/24 |
Field of Search: |
29/897.312,897.34,469.5,527.1,527.4
52/171.3,172,786.1,786.13,656.5,656.6
72/379.2
156/107,109
|
References Cited
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3974823 | Aug., 1976 | Patil.
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4132539 | Jan., 1979 | Jeffries.
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4270688 | Jun., 1981 | Janssens et al.
| |
4318959 | Mar., 1982 | Evans et al.
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4350515 | Sep., 1982 | Stewart.
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4431691 | Feb., 1984 | Greenlee.
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4464874 | Aug., 1984 | Shea, Jr. et al.
| |
4520611 | Jun., 1985 | Shingu et al.
| |
4574553 | Mar., 1986 | Lisec.
| |
4590240 | May., 1986 | Streeter et al.
| |
4610771 | Sep., 1986 | Gillery.
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4622249 | Nov., 1986 | Bowser.
| |
4649685 | Mar., 1987 | Wolf et al.
| |
4780164 | Oct., 1988 | Rueckheim et al.
| |
4780521 | Oct., 1988 | Duck et al.
| |
4806220 | Feb., 1989 | Finley.
| |
4807419 | Feb., 1989 | Hodek et al.
| |
4807439 | Feb., 1989 | Hain et al.
| |
4808452 | Feb., 1989 | McShane.
| |
4817354 | Apr., 1989 | Bayer.
| |
4831799 | May., 1989 | Glover et al.
| |
4853256 | Aug., 1989 | Obringer et al.
| |
4853257 | Aug., 1989 | Henery.
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4873803 | Oct., 1989 | Rundo.
| |
4933032 | Jun., 1990 | Kunert.
| |
4950344 | Aug., 1990 | Glover et al.
| |
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| |
5177916 | Jan., 1993 | Misera et al.
| |
5255481 | Oct., 1993 | Misera et al.
| |
Foreign Patent Documents |
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|
0 430 889 | Nov., 1990 | EP.
| |
0 403 058 | Dec., 1990 | EP.
| |
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|
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| |
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| |
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| |
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| |
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| |
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| |
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| |
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|
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| |
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| |
Other References
"Super Spacer.TM.", Edgetech I.G. Ltd., May 1988.
Glover et al.; "Super Spacer.TM. Technical Report", Edgetech I.G. Ltd., May
1988.
"Superglass.TM. System With Heat Mirror Film".
"Introducing Super Spacer.TM. PIB".
Wright et al., "Thermal Resistance Measurement of Glazing System Edge-Seals
and Seal Materials Using a Guarded Heater Plate Apparatus".
"What Is Warm Edge Technology"; Glass Digest, pp. 74-76; Mar. 1991.
Advertisement from Lockformer Company (no Date).
|
Primary Examiner: Gorski; Joseph M.
Attorney, Agent or Firm: Lepiane; Donald C.
Parent Case Text
RELATED APPLICATION
This application is a continuation of application Ser. No. 08/086,286,
filed Jul. 1, 1993, now abandoned, which is a division of application Ser.
No. 07/686,956, filed Apr. 18, 1991, now abandoned, which is a
continuation-in-part of application Ser. No. 07/578,696, filed on Sep. 4,
1990, now abandoned.
Claims
What is claimed is:
1. A method of making an insulating unit having a low thermal edge,
comprising the steps of:
forming a metal spacer frame, the spacer frame having a base, a first
upright leg connected to the base and a second upright leg connected to
the base and spaced from the first upright leg, the base having an inner
surface facing the space between the upright legs and a surface opposite
to the inner surface defined as an outer surface, the outer surface being
generally flat, the first and second upright legs and outer surface of the
base having a generally U-shaped configuration with the first and second
legs only interconnected by the base;
providing a moisture and gas impervious sealant on an outer surface of the
first and second upright legs wherein the spacer frame and sealant provide
an edge assembly;
selecting the metal and physical dimensions of the spacer frame and
sealant, such that the edge assembly is provided with a RES-value of at
least 10 measured using ANSYS program, and
securing a first sheet by the sealant on the outer surface of the first
upright leg and a second sheet by the sealant on the outer surface of the
second upright leg, thereby providing a sealed compartment between the
sheets, wherein the sheets have a center and wherein the spacer frame is
out of physical contact with the sheets with the inner surface of the base
of the spacer frame facing the center of the sheets, and the sealant
between the outer surface of the first and second upright legs and the
respective adjacent sheets has a high resistance to the passage of gas
between the outer surface of the first and second upright legs and the
respective adjacent sheets, wherein a thermal conducting path between the
sheets of the unit is only through the edge assembly, thereby providing
the spacer frame, sealant and sheets as a unit with a RES-value of at
least 10 at marginal edges of the unit.
2. The method as set forth in claim 1 wherein the spacer frame is made of
low thermal conducting metal.
3. The method as set forth in claim 2 wherein the metal of the spacer frame
is stainless steel.
4. The method of claim 3 wherein the sheets are glass sheets, and the
sealant form a compartment and further including the step of filling the
compartment with an insulating gas.
5. The unit of claim 4 wherein the rate of gas loss from the compartment is
less than 5% per year measured pursuant to European procedure DIN 52293.
6. The method of claim 1 wherein the RES-value is at least 79.
7. The method of claim 1 wherein the RES-value is at least 100.
8. The method as set forth in claim 1 wherein the unit has at least one
corner and said step of forming a metal spacer frame includes the steps
of:
providing a spacer stock having a length sufficient to provide the spacer
frame, the spacer stock having the first and second upright legs connected
to the base and material removed from each of the first and second upright
legs thereby providing a material void in each of the first and second
upright legs at a position on the spacer stock expected to form the at
least one corner when the spacer frame is formed;
bending the spacer stock at the material void, thereby decreasing the
material void by bringing portions of the upright legs on each side of the
void toward one another, thereby providing the at least one corner wherein
at least the base at the at least one corner is continuous; and
joining ends of the spacer stock together.
9. The method as set forth in claim 8 further including the step of
providing a moisture pervious material having desiccant therein on the
base of the spacer stock between the upright legs, wherein the moisture
pervious material containing the desiccant is a component of the edge
assembly, and the metal of the spacer frame, the sealant and the material
containing the desiccant provide the edge assembly with the RES-value of
at least 10.
10. The method as set forth in claim 1 wherein the sealant is a moisture
impervious adhesive sealant, each of the upright legs of the spacer frame
have a height as viewed in cross section of about at least 0.010 inch and
the layers of the moisture impervious adhesive sealant between the upright
legs of the spacer frame and adjacent sheet has a thickness of about 0.010
inch, thereby providing the unit with a long diffusion path.
11. The method as set forth in claim 1 wherein the unit has at least one
corner and said step of forming a metal spacer frame includes the steps
of:
providing a spacer stock having a length sufficient to provide the spacer
frame, the spacer stock having the first and second upright legs connected
to the base;
bending the spacer stock at the expected at least one corner, thereby
moving material of the upright legs toward one another over the inner
surface of the base; and
joining ends of the spacer stock together.
12. The method according to claim 11, wherein the spacer frame has four
corners, and including repeating the bending step at least three times.
13. The method as set forth in claim 1 wherein the sheets have peripheral
dimensions greater than peripheral dimensions of the spacer frame such
that after the securing step a peripheral channel is defined by the outer
surface of the base of the spacer frame and marginal edge portions of the
sheets, further including the steps of providing an adhesive in the
peripheral channel and providing a moisture pervious material containing a
desiccant on the inner surface of the base of the spacer frame between the
upright legs wherein the moisture pervious material containing the
desiccant and the adhesive in the peripheral channel are components of the
edge assembly and the metal of the spacer frame, the sealant, the moisture
pervious adhesive containing the desiccant and the adhesive in the
peripheral channel provide the edge assembly with the RES-value of at
least 10.
Description
The unit taught in this application may be fabricated using the spacer and
spacer frame disclosed in U.S. patent application Ser. No. 07/578,697
filed on Sep. 4, 1990, in the names of Stephen C. Misera and William
Siskos and entitled A SPACER AND SPACER FRAME FOR AN INSULATING GLAZING
UNIT AND METHOD OF MAKING SAME.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an insulating glazing unit and a method of making
same and, in particular, to an insulating glazing unit having an edge
assembly to provide the unit with a low thermal conducting edge, i.e. high
resistance to heat flow at the edge of the unit.
2. Discussion of Available Insulating Units
It is well recognized that insulating glazing units reduce heat transfer
between the outside and inside of a home or other structures. A measure of
insulating value generally used is the "U-value". The U-value is the
measure of heat in British Thermal Unit (BTU) passing through the unit per
hour (Hr)-square foot (Sq. Ft.)-degree Fahrenheit (.degree.F)
##EQU1##
As can be appreciated the lower the U-value the better the thermal
insulating value of the unit, i.e. higher resistance to heat flow
resulting in less heat conducted through the unit. Another measure of
insulating value is the "R-value" which is the inverse of the U-value.
Still another measure is the resistance (RES) to heat flow which is stated
in Hr-.degree.F per BTU per inch of perimeter of the unit
##EQU2##
In the past the insulating property, e.g. U-value given for an insulating
unit was the U-value measured at the center of the unit. Recently it has
been recognized that the U-value of the edge of the unit must be
considered separately to determine the overall thermal performance of the
unit. For example, units that have a low center U-value and high edge
U-value during the winter season exhibit no moisture condensation at the
center of the unit, but may have condensation or even a thin line of ice
at the edge of the unit near the frame. The condensation or ice at the
edge of the unit indicates that there is heat loss through the unit and/or
frame i.e. the edge has a high U-value. As can be appreciated, when the
condensate or water from the melting ice runs down the unit onto wooden
frames, the wood, if not properly cared for, will rot. Also, the larger
temperature differences between the warm center and the cold edge can
cause greater edge stress and glass breakage. The U-values of framed and
unframed units and methods of determining same are discussed in more
detail in the section entitled "Description of the Invention."
Through the years, the design of and construction materials used to
fabricate insulating glazing units, and the frames have improved to
provide framed units having low U-values. Several types of units presently
available, and center and edge U-values of selected ones, are considered
in the following discussion.
Insulating glass edge units which are characterized by (1) the edges of the
glass sheets welded together, (2) a low emissivity coating on one sheet
and (3) argon in the space between the sheets are taught, among other
places, in U.S. patent application Ser. No. 07/468,039 assigned to PPG
Industries, Inc. filed on Jan. 22, 1990, in the names of P. J. Kovacik et
al. and entitled "Method of and Apparatus for Joining Edges of Glass
Sheets, One of Which Has an Electroconductive Coating and the Article Made
Thereby." The units taught therein have a measured center U-value of about
0.25 and a measured edge U-value of about 0.55. Although insulating units
of this type are acceptable, there are limitations. For example, special
equipment is required to heat and fuse the edges of the glass sheets
together, and tempered glass is not used in the construction of the units.
In U.S. Pat. No. 4,807,439 there is taught an insulting unit marketed by
PPG Industries, Inc. under the registered trademark SUNSEAL. The unit has
a pair of glass sheets spaced about 0.45 inch (1.14 centimeters) apart
about an organic edge assembly and air in the compartment between the
sheets. A unit so constructed is expected to have a measured center
U-value of about 0.35 and an edge U-value of about 0.59. Although
providing insulating gas e.g. argon in the unit would lower the center and
edge U-values, the argon in time would diffuse through the organic edge
assembly raising the center and edge U-values to those values previously
stated.
The unit of U.S. Pat. No. 4,831,799 has an organic edge assembly and a gas
barrier coating, sheet or film at the peripheral edge of the unit to
retain argon in the unit. The thermal performance of the unit is discussed
in column 5 of the patent. U.S. Pat. Nos. 4,431,691 and 4,873,803 each
teach a unit having a pair of glass sheets separated by an edge assembly
having an organic bead having a thin rigid member embedded therein.
Although the units of these patents have acceptable U-values, they have
drawbacks. More particularly, the units have a short length, high
resistance diffusion path. The diffusion path is the distance that gas,
e.g. argon, air, or moisture has to travel to exit or enter the
compartment between the sheets. The resistance of the diffusion path is
determined by the permeability, thickness and length of the material. The
units taught in U.S. Pat. Nos. 4,831,799; 4,431,691 and 4,873,803 have a
high resistance, short diffusion path between the metal strip or spacing
means and the glass sheets; the remainder of the edge assembly has a low
resistance, long length diffusion path.
In U.S. Pat. No. 3,919,023, there is taught an edge assembly for an
insulating unit that provides a high resistance, long length diffusion
path that may be used to minimize the loss of argon. A limitation of the
edge assembly of the patent is the use of a metal strip around the outer
marginal edges of the unit. This metal strip conducts heat around the edge
of the unit, and the unit is expected to have a high edge U-value.
It was mentioned that the effect of the frame U-value on the window edge
U-value should be taken into account; however, a detailed discussion of
frames having low U-value is omitted because the instant invention is
directed to an insulating glazing unit that has low center and edge
U-values, is easy to construct, does not have the limitations or drawbacks
of the presently available insulating glazing units, and may be used with
any frame construction.
SUMMARY OF THE INVENTION
The invention covers an insulating unit having a pair of glass sheets
separated by an edge assembly to provide a sealed compartment between the
sheets having a gas therein. The edge assembly includes a spacer that is
structurally sound to maintain the glass sheets in a fixed spaced
relationship and yet accommodates a certain degree of thermal expansion
and contraction which typically occurs in the several component parts of
the insulating glazing unit. A diffusion path having resistance to the gas
in the compartment e.g. a long thin diffusion path, is provided between
the spacer and the glass sheets, and the edge assembly has a high RES
value at the unit edge as determined using the ANSYS program.
The invention also covers a method of making an insulating unit. The method
includes the steps of providing an edge assembly between a pair of glass
sheets to provide a compartment therebetween. The edge assembly is
fabricated by providing a pair of glass sheets; selecting a structurally
resilient spacer, sealant materials and moisture pervious desiccant
containing material to provide an edge assembly having a high RES as
determined using the ANSYS program and a long thin diffusion path. The
glass sheets, spacer, sealant material and desiccant containing materials
are assembled to provide an insulating unit having a high RES at the edge
as measured using the ANSYS, program.
The preferred insulating unit of the invention has an environmental
coating, e.g. a low-E coating on at least one sheet surface. Adhesive
sealant on each of the outer surfaces of the spacer having a "U-shaped"
cross section secures the sheets to the spacer. A strip of moisture
pervious adhesive having a desiccant is provided on the inner surface of
the spacer.
Further, the invention covers a spacer that may be used in the insulating
unit. The spacer includes a structurally resilient core e.g. a plastic
core having a moisture/gas impervious film e.g. a metal film or a
halogenated polymeric film such as polyvinylidene chloride or flouride or
polyvinyl chloride or polytrichlorofluoro ethylene.
Additionally, the spacer may be made entirely from a polymeric material
having both structural resiliency and moisture/gas impervious
characteristics such as a halogenated polymeric material including
polyvinylidene chloride or flouride or polyvinyl chloride or
polytrichlorofluoro ethylene.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 thru 4 are cross sectional views of edge assemblies of prior art
insulating units.
FIG. 5 is a plan view of an insulating unit having a generic spacer
assembly.
FIG. 6 is a view taken along lines 6--6 of FIG. 5.
FIG. 7 is the left half of the view of FIG. 6 showing heat flow lines
through the unit.
FIG. 8 is a view similar to the view of FIG. 7 having the heat flow lines
removed.
FIG. 9 is a graph showing edge temperature distribution for units having
various type of edge assemblies.
FIG. 10 is a sectional view of an edge assembly incorporating features of
the invention.
FIG. 11 is a cross section of another embodiment of a spacer of the instant
invention.
FIG. 12 is a view of an edge strip incorporating features of the invention
having a bead of a moisture and/or gas pervious adhesive having a
desiccant.
FIG. 13 is a side elevated view of a roll forming station to form the edge
strip of FIG. 12 into spacer stock incorporating features of the instant
invention.
FIGS. 14 thru 16 are views taken along lines 14 thru 16 respectively of
FIG. 13.
FIG. 17 is a view of a continuous corner of a spacer frame of the instant
invention made using the spacer section shown in FIG. 18.
FIG. 18 is a partial side view of a section of spacer stock notched and
creased prior to bending to form the continuous corner of the spacer frame
shown in FIG. 17 in accordance to the teachings and incorporating features
of the inventions.
FIG. 19 is a view similar to the view of FIG. 18 illustrating another
continuous corner of a spacer frame incorporating features of the
invention.
FIG. 20 is a view similar to the view of FIG. 10 showing another embodiment
of the invention.
DESCRIPTION OF THE INVENTION
In the following discussion like numerals refer to like elements, and the
units are described having two glass sheets; however, as is appreciated by
those skilled in the art, units with more than two sheets as shown in FIG.
20 are also contemplated.
With reference to FIGS. 1-4 there are shown four general types of prior art
edge assemblies used in the construction of insulated glazing units. Unit
10 of FIG. 1 includes a pair of glass sheets 12 and 14 spaced from one
another by an edge assembly 16 to provide a compartment 18 between the
sheets. The edge assembly 16 includes a hollow metal spacer 20 having a
desiccant 22 therein to absorb any moisture in the compartment and holes
23 (only one shown in FIG. 1) providing communication between the
desiccant and the compartment. The edge assembly 16 further includes an
adhesive type sealant 24 e.g. silicon at the lower section of the spacer
20 as viewed in FIG. 1 to secure the spacer 20 and the glass sheets
together and a sealant 25 e.g. a butyl sealant at the upper section of the
spacer 20 to prevent the egress of insulating gas in the compartment 18.
The edge assembly 16 of the unit 10 is similar to the type of units sold
by Cardinal Class and also similar to the insulating units taught in U.S.
Pat. Nos. 2,768,475; 3,919,023; 3,974,823; 4,520,611 and 4,780,164 which
teachings are hereby incorporated by reference.
Unit 30 in FIG. 2 includes the glass sheets 12 and 14 having their edges
welded together at 32 to provide the compartment 18. One of the glass
sheets e.g. sheet 12 has a low emissivity coating 34. The unit 30 shown in
FIG. 2 is similar to the insulating units sold by PPG Industries, Inc.
under its trademark OptimEdge and is also similar to the units taught in
U.S. Pat. Nos. 4,132,539 and 4,350,515 and in U.S. patent application Ser.
No. 07/468,039 filed on Jan. 22, 1990,discussed above, which teachings are
hereby incorporated by reference.
With reference to FIG. 3 there is shown unit 50 taught in U.S. Pat. No.
4,831,799, which teachings are hereby incorporated by reference. The unit
50 has the glass sheets 12 and 14 separated by an edge assembly 52 to
provide the compartment 18. The edge assembly 52 includes a moisture
pervious foam material 54 having a desiccant 56 therein to absorb moisture
in the compartment 18, a moisture impervious sealant 58 to prevent
moisture in the air from moving into the compartment 18 and a gas barrier
coating, sheet or film 60 between the foam material 54 and sealant 58 to
prevent egress of the insulating gas in the compartment 18. Units similar
to the unit 50 are taught in U.S. Pat. No. 4,807,419 which teachings are
hereby incorporated by reference.
In FIG. 4 there is shown unit 70 taught in U.S. Pat. Nos. 4,431,691 and
4,873,803 which teachings are hereby incorporated by reference. The unit
70 has the glass sheets 12 and 14 separated by an edge assembly 72 to
provide the compartment 18. The edge assembly 72 includes a moisture
pervious adhesive 74 having a desiccant 76 and a metal member 78 therein.
Before teaching the construction of the insulating unit, more particularly
the edge assembly of the instant invention, a discussion of the heat
transfer through an insulated unit is deemed appropriate to fully
appreciate the instant invention. In the following discussion the U-value
will be used to compare or rate heat transfer i.e. resistance to heat flow
through a glazing unit to reduce heat loss. As is appreciated by those
skilled in the art the lower the U-value the less heat transfer and vice
versa. The U-value for an insulating unit can be determined from the
following equation.
Ut=(Ac/At)Uc+(Ae/At)Ue+(Af/At)Uf (1)
where U is the measure of heat transfer in British Thermal
Unit/hour-square foot-.degree.F (BTU/Hr-Sq. Ft.-.degree.F.)
A is area under consideration in square feet
c designates the center of the unit
e designates the edge of the unit
f designates the frame
t is total unit value of the parameter under discussion
Shown in FIGS. 5 and 6 is a generic insulating unit 90 having the glass
sheets 12 and 14 separated by an edge assembly 92 to provide the
compartment 18. The edge assembly 92 is considered for the purposes of
this discussion a generic edge assembly and is not limited by design. With
specific reference to FIG. 5, the unit 90 for purposes of the discussion
has an edge area 94 which is the area between the peripheral edge 95 of
the unit and a position about 3.0 inches (7.62 centimeters) in from the
peripheral edge, and a central area 96. The interface between the edge
area 94 and center area 96 of the unit 90 is shown in FIG. 5 by dotted
lines 98.
The left half of unit 90 shown in FIG. 6 is shown in FIG. 7 having the
numerals removed for purposes of clarity during the following discussion
relating to heat transfer through the unit. With reference to FIGS. 5, 6
and 7 as required, during the winter season, heat from inside an enclosure
e.g. a house moves through the edge area 94 and center area 96 of the unit
90 to the outside. Referring now to FIG. 7, at the center area 96 of the
unit, the heat flow pattern is generally perpendicular to the isotherm
which is the major surfaces of the glass sheets 12 and 14 and is
illustrated in FIG. 7 by arrowed lines 100. The direction of the heat flow
pattern changes as the peripheral edge 95 of the unit is approached as
illustrated by arrowed lines 102, until at the peripheral edge 95 of the
unit the heat flow pattern is again perpendicular to the major surface of
the glass sheets as illustrated by arrowed lines 104. As can be
appreciated by those skilled in the art, a frame mounted about the
periphery of the unit has an effect on the flow patterns, in particular,
flow patterns 102 and 104. For purposes of this discussion the effect of
the frame on flow patterns 102 and 104 is omitted, and the above
discussion is considered sufficient to provide a background to appreciate
the instant invention.
The heat flow through the center area 96 of the unit 90 may be modified by
changes in the thermal properties of sheets 12 and 14, the distance
between the sheets and gas in the compartment 18. Consider now the
distance between the sheets i.e. the compartment spacing. Compartments
having a spacing between about 0.250-0.500 inch (0.63-1.27 centimeters)
are considered acceptable to provide an insulating gas layer with the
preferred spacing depending on the insulating gases used. Krypton gas is
preferred at the low range, air and argon are preferred at the upper
range. In general, below 0.250 inch (0.63 centimeter) the spacing is not
wide enough e.g. for air or argon gas to provide a significant insulating
gas layer and above 0.500 inch (1.27 centimeters), gas currents e.g. using
krypton gas in the compartment have sufficient mobility to allow
convection thereby moving heat between the glass surfaces, e.g. between
the glass surface facing the house interior to the glass surface facing
the house exterior.
As previously mentioned, heat flow through the unit may also be modified by
the type of gas used in the compartment. For example, using a gas that has
a high thermal insulating value increases the performance of the unit, in
other words it decreases the U-value at the center and edge areas of the
unit. By way of example, but not limiting to the invention, argon has a
higher thermal insulating value than air. Everything else relating to the
construction of the unit being equal, using argon would lower the U-value
of the unit.
Another technique to modify the thermal insulating value of the center area
is to use sheets having high thermal insulating values and/or sheets
having low emissivity coatings. Types of low emissivity coatings that may
be used in the practice of the invention are taught in U.S. Pat. Nos.
4,610,771; 4,806,220; and 4,853,256 which teachings are hereby
incorporated by reference. Also increasing the number of glass sheets
increases the number of compartments thereby increasing the insulating
effect at the center and edge areas of the unit.
The discussion will now be directed to the thermal loss at the edge area of
the unit. With reference to FIG. 8 there is shown an edge portion of the
unit 90 shown in FIGS. 5 and 6. The letters A and E are the points where
heat flow is generally perpendicular to the glass surfaces. As the edge of
the unit is approached the glass begins to act as an extended surface
relative to the edge and causes the heat flow paths 100 to curve or bend
at the edge of the unit as illustrated in FIG. 7 by numerals 102. This
curvature occurs in the edge area 94 shown in FIGS. 6 and 7. Between the
letters B and D the flow of heat is primarily resisted by the edge
assembly 92 rather than the glass at the unit edge. With reference to FIG.
9 curves 120, 130 and 140 show the edge heat loss for different types of
edge assemblies. FIG. 9 should not be interpreted as an absolute
relationship but as a general guide to better understand the heat flow
through the edge assembly. Curve 120 illustrates the heat loss pattern for
an edge assembly that is highly heat conductive e.g. an aluminum spacer
generally used in the construction of edge assemblies of the types shown
in FIG. 1. Curve 130 illustrates the heat loss pattern for an edge
assembly that is less heat conductive than an edge assembly having an
aluminum spacer e.g. an edge assembly having a plastic spacer similar to
the construction of the edge assembly shown in FIG. 3. Line 140
illustrates the edge heat loss pattern for a glass edge unit of the type
shown in FIG. 2. Although not limiting to the invention, the edge assembly
incorporating features of the invention is expected to provide a heat loss
pattern similar to curve 140 and heat loss patterns within the shaded
areas between curves 130 and 140.
As can be seen in FIG. 9, the profile for an aluminum spacer represented by
the curve 120 shows that the aluminum spacer at the edge of the unit
(between points A and C) offers little resistance to heat flow thus
allowing a cooler edge at the surface of the unit inside the house. The
profile for an organic e.g. polymeric spacer represented by the curve 130
shows the organic spacer to have a high resistance to heat flow allowing
for a warmer glass surface inside the house resulting in reduced heat loss
at the edge of the unit. This is particularly illustrated by the curve 130
between points A and C. Edges of welded glass sheets e.g. as shown in FIG.
2 offer more resistance than the metal type spacer assembly but less than
the plastic type edge assembly. The temperature distribution of edge
welded units between points A and C is represented by the line 140 which
is between lines 120 and 130 between points A and C on the graph of FIG.
9.
The heat loss for an edge assembly using a metal spacer, in particular an
aluminum spacer is greater than for glass because the aluminum spacer has
a higher thermal conductivity (aluminum is a better conductor of heat than
glass or organic materials). The effect of the higher thermal conductivity
of the aluminum spacer is also evident at point D which shows the curve
120 for the aluminum spacer to have a higher temperature than the curve
140 or the curve 130 at the outside surface of the unit. The heat to
maintain the higher temperature at D for the aluminum spacer is conducted
from inside the house thereby resulting in a heat loss at the edge of the
unit greater than the edge heat loss for units having glass or organic
spacers, and greater than the edge assembly of the invention as will be
discussed in detail below.
The heat loss for an edge assembly having an organic spacer is less than
the heat loss for edge assemblies having metal spacers or welded glass
because the organic spacer has a lower thermal conductivity. The effect of
the lower thermal conductivity of the organic spacer is shown by line 130
at point D which has a lower temperature than the glass and metal spacers
illustrating that conductive heat loss through the organic spacer is less
than for glass and metal spacers.
A phenomenon of units having high edge heat loss is that on very cold days,
a thin layer of condensation or ice forms at the inside of the unit at the
frame. This ice or condensate may be present even though the center of the
unit is free of moisture.
As was discussed, units that have argon in the compartment and polymeric
edge assemblies may have an initial low U-value, but as time passes, the
U-value increases because polymeric spacers as a general rule do not
retain argon. To retain argon an additional film such as that taught in
U.S. Pat. No. 4,831,799 is required. The drawback of the unit of this U.S.
Pat. No. 4,831,799 is that the film has a short diffusion path as was
discussed supra. As can be appreciated argon retention can be improved by
selection of materials e.g. hot melt adhesive sealants such as HB Fuller
1191, HB Fuller 1081A and PPG Industries, Inc. 4442 butyl sealant retain
argon better than most polyurethane adhesives.
With reference to FIG. 10 there is shown insulating unit 150 having edge
assembly 152 incorporating features of the invention to space the glass
sheets 12 and 14 to provide the compartment 18. The edge assembly 152
includes a moisture and/or gas impervious adhesive type sealant layer 154
to adhere the glass sheets 12 and 14 to legs 156 of metal spacer 158. The
sealant layers 154 act as a barrier to moisture entering the unit and/or a
barrier to gas e.g. insulating gas such as argon from exiting the
compartment 22. With respect to the loss of the fill gas from the unit, in
practice the length of the diffusion path and thickness of the sealant
bead are chosen in combination with the gas permeability of sealant
material so that the rate of loss of the fill gas matches the desired unit
performance lifetime. The ability of the unit to contain the fill gas is
measured using a European procedure identified as DIN 52293. Preferably,
the rate of loss of the fill gas should be less than 5% per year and more
preferably it should be less than 1% per year.
With respect to the ingress of moisture into the unit, the geometry of the
sealant bead is chosen so that the amount of moisture permeating through
the perimeter parts (i.e. sealant bead and spacer) is a quantity able to
be absorbed into the quantity of desiccant within the unit over the
desired unit lifetime. The preferred adhesive sealant to be used with the
spacer of FIGS. 10 and 11 should have a moisture permeability of less than
20 gm mm/M.sup.2 day using ASTM F 372-73. More preferably, the
permeability should be less than 5 gm mm/M.sup.2 day.
The relationship between the amount of desiccant in the unit and the
permeability of the sealant (and its geometry) may be varied depending on
the overall desired unit lifetime.
An additional adhesive sealant type layer or structural adhesive layer 155
e.g. but not limited to silicone adhesive and/or hot melts may be provided
in the perimeter groove of the unit formed by middle leg 157 of the spacer
and marginal edges of the glass sheets. As can now be appreciated the
sealant is not limiting to the invention and may be any of the types known
in the art e.g. the type taught in U.S. Pat. No. 4,109,431 which teachings
are hereby incorporated by reference. A thin layer 160 of a moisture
pervious adhesive having a desiccant 162 therein to absorb moisture in the
compartment 18 is provided on the inner surface of the middle leg 157 of
the spacer 158 as viewed in FIG. 10. The desiccant may also be placed
along the inner surface of the legs 156 as well as the middle leg 157. The
permeability of the adhesive layer 160 is not limiting to the invention
but should be sufficiently permeable to moisture within compartment 18 so
that the desiccant therein can absorb moisture within the compartment.
Adhesive materials having a permeability of greater than 2 gm mm/M.sup.2
day as determined by the above referred to ASTM F 372-73 may be used in
the practice of the invention. The edge assembly 152 provides the unit 150
with a low thermal conductive path through the edge i.e. a high resistance
to heat loss, a long diffusion path and structural integrity with
sufficient structural resilience to accommodate a certain degree of
thermal expansion and contraction which typically occurs in the several
component parts of the insulating glazing unit.
To fully appreciate the high resistance to heat loss of the edge assembly
of the instant invention, the following discussion of the mechanism of
thermal conductivity through the edge of an insulated unit is presented.
The heat loss through an edge of a unit is a function of the thermal
conductivity of the materials used, their physical arrangement, the
thermal conductivity of the frame and surface film coefficient. Surface
film coefficient is transfer of heat from air to glass at the warm side of
the unit and heat transfer from glass to air on the cold side of the unit.
The surface film coefficient depends on the weather and the environment.
Since the weather and environment are controlled by nature and not by unit
design, no further discussion is deemed necessary. The frame effect will
be discussed later leaving the present discussion to the thermal
conductivity of the materials at the unit edge and their physical
arrangement.
The resistance of the edge of the unit to heat loss for an insulating unit
having sheet material separated by an edge assembly is given by equation
(2).
RHL=G.sub.1 +G.sub.2 + . . . +G.sub.n +S.sub.1 +S.sub.2 + . . . +S.sub.n
(2)
where RHL is the resistance to edge heat loss at the edge of the unit in
hour -.degree. F/BTU/inch of unit perimeter (Hr-.degree.F/BTU/in.)
G is the resistance to heat loss of a sheet in Hr-.degree.F/BTU/in.
S is the resistance to heat loss of the edge assembly in
Hr-.degree.F/BTU/in.
For an insulating unit having two sheets separated by a single edge
assembly equation (2) may be rewritten as equation (3).
RHL=G.sub.1 +G.sub.2 +S.sub.1 (3)
The thermal resistance of a material is given by equation (4).
R=L/KA (4)
where R is the thermal resistance in Hr-.degree.F/BTU/in.
K is thermal conductivity of the material in BTU/hour-inch-.degree.F.
L is the thickness of the material as measured in inches along an axis
parallel to the heat flow.
A is the area of the material as measured in square inches along an axis
transverse to the heat flow/in. of perimeter.
The thermal resistance for components of an edge assembly that lie in a
line substantially perpendicular or normal to the major surface of the
unit is determined by equation (5).
S=R.sub.1 +R.sub.2 + . . . +R.sub.n (5)
where S and R are as previously defined.
In those instances where the components of an edge assembly lie along an
axis parallel to the major surface of the unit, the thermal resistance (S)
is defined by the following equation (6).
##EQU3##
where R is as previously defined.
Combining equations (3), (5) and (6) the resistance of the edge of the unit
150 shown in FIG. 10 to heat flow may be determined by following equation
(7).
##EQU4##
where RHL is as previously defined, R.sub.12 and R.sub.14 are the thermal
resistance of the glass sheets,
R.sub.154 is the thermal resistance of the adhesive layer 154,
R.sub.155 is the thermal resistance of the adhesive layer 155,
R.sub.156 is the thermal resistance of the outer legs 156 of the spacer
158,
R.sub.157 is the thermal resistance of the middle leg 157 of the spacer
158, and
R.sub.160 is the thermal resistance of the adhesive layer 160.
Although equation (7) shows the relation of the components to determine
edge resistance to heat loss, Equation 7 is an approximate method used in
standard engineering calculations. Computer programs are available which
solve the exact relations governing heat flow or resistance to heat flow
through the edge of the unit.
One computer program that is available is the thermal analysis package of
the ANSYS program available from Swanson Analysis Systems Inc. of Houston,
Pa. The ANSYS program was used to determine the resistance to edge heat
loss or U-value for units similar to those shown in FIGS. 1-4.
The edge U-value, defined previously, while being a measure of the overall
effect demonstrating the utility of the invention is highly dependent on
certain phenomena that are not limiting to the invention such as film
coefficients, glass thickness and frame construction. The discussion of
the edge resistance of the edge assembly (excluding the glass sheets) will
now be considered. The edge resistance of the edge assembly is defined by
the inverse of the flow of heat that occurs from the interface of the
glass and sealant layer 154 at the inside side of the unit to the
interface of glass and sealant layer 154 at the outside side of the unit
per unit increment of temperature, per unit length of edge assembly
perimeter. The glass sealant interfaces are assumed to be isothermal to
simplify the discussion. Support for the above position may be found,
among other places, in the paper entitled Thermal Resistance Measurements
of Glazing System Edge-Seals and Seal Materials Using a Guarded Heater
Plate Apparatus written by J. L. Wright and H. F. Sullivan ASHRAE
TRANSACTIONS 1989, V.95, Pt. 2.
In the following discussion and in the claims, a parameter of interest is
the resistance to heat flow of the edge assembly per unit length of
perimeter ("RES").
As mentioned above, the ANSYS finite element code was used to determine the
RES. The result of the ANSYS calculation is dependent on the assumed
geometry of the cross section of the edge assembly and the assumed thermal
conductivity of the constituents thereof. The geometry of any such cross
section can easily be measured by studying the unit edge assembly. The
thermal conductivity of the constituents or the edge assembly RES value
can be measured as shown in ASHRAE TRANSACTIONS identified above. The
following thermal conductivity values for edge assembly materials are
given in the article. Additional values may be found in Principles of Heat
Transfer 3rd ed. by Frank Kreith.
______________________________________
Material Thermal Conductivity
______________________________________
Butyl .24 W/mC (.011 BTU/hr-in-.degree.F.)
Silicone .36 W/mC (.017 BTU/hr-in-.degree.F.)
Polyurethene .31 W/mC (.014 BTU/hr-in-.degree.F.)
304 stainless steel
13.8 W/mC (.667 BTU/hr-in-.degree.F.)
Aluminum 202. W/mC (9.75 BTU/hr-in-.degree.F.)
______________________________________
Let us now consider the RES calculated for edge assemblies of the units of
FIGS. 1-4. The construction of the edge assembly 16 of the unit 10 of FIG.
1 included a hollow aluminum spacer 20 between the glass sheets; the
spacer had a wall thickness of about 0.025 inch (0.06 centimeter), a side
length perpendicular to the major surface of the glass sheets 12 and 14 of
about 0.415 inch (1.05 centimeters), and a side length generally parallel
to the major surface of the glass sheets 12 and 14 of about 0.3 inch (0.76
centimeter); adhesive layers 24 of butyl having a thickness of about 0.003
inch (0.008 centimeter); and a silicone structural seal 16 filling the
cavity formed by the spacer 20 and glass sheets 12 and 14. The edge
assembly RES-value of the unit (10) constructed as above discussed using
the ANSYS program was calculated to be 4.65 hr-.degree.F/BTU per inch of
perimeter.
The construction of the edge assembly 32 of the unit 30 of FIG. 2 included
a pair of glass sheets spaced about 0.423 inch (1.07 centimeters) apart;
an edge wall designated by number 32 having a thickness of about 0.090
inch (0.229 centimeter). The edge assembly RES-value of the unit 30
constructed as described above using the ANSYS program was calculated to
be 104 hr-.degree.F/BTU per inch of perimeter.
The construction of the edge assembly 52 of the unit 50 of FIG. 3 included
a pair of glass sheets 12 and 14 spaced about 0.50 inch (1.27 centimeters)
apart; a desiccant filled foam structural member about 0.25 inch (0.64
centimeter) thick adhered to the glass surfaces; an aluminum coated
plastic diffusion barrier and a butyl edge seal about 0.25 inch (0.64
centimeter) thick. The aluminum coating between the foam member and seal
was too thin for accurate measurement. The edge assembly RES-value of the
unit 50 constructed as above described using the ANSYS program was
calculated to be 104.0 hr-.degree.F/BTU per inch of perimeter.
A unit similar to the unit 50 of FIG. 3 having a pair of glass sheets 12
and 14 spaced 0.45 inch (1.143 centimeters) apart; an adhesive layer 54 of
silicone having a thickness of about 0.187 inch (0.475 centimeter) with
desiccant therein; a moisture impervious sealant 58 of butyl having a
thickness of about 0.187 inch (0.475 centimeter) is expected using the
ANSYS program to have an edge assembly RES-value using the ANSYS program
of about 84.7 hr-.degree.F/BTU per inch of perimeter. A comparison of the
edge assembly RES-value for the different constructions of units of the
type shown in FIG. 3 are given to show the effect material changes and
dimensions have on the edge assembly RES-value.
The construction of the edge assembly of the unit 70 of FIG. 4 included a
pair of glass sheets spaced about 0.45 inch (1.143 centimeters) apart; an
adhesive butyl edge seal about 0.312 inch (0.767 centimeter) wide with a
desiccant and an aluminum spacer about 0.010 inch (0.025 centimeter) thick
imbedded therein. The edge assembly RES-value of the unit 70 constructed
as above described using the ANSYS program was calculated to be 4.50
hr-.degree.F/BTU per inch of perimeter.
The construction of the edge assembly 150 of the instant invention shown in
FIG. 10 included a pair of glass sheets spaced about 0.47 inch (1.20
centimeters) apart; a polyisobutylene layer 154 which is moisture and
argon impervious had a thickness of about 0.010 inch (0.254 centimeter)
and a height as viewed in FIG. 10 of about 0.250 inch (0.64 centimeter); a
304 stainless steel U-shaped channel 156 had a thickness of about 0.007
inch (0.018 centimeter), the middle or center leg had a width as viewed in
FIG. 10 of about 0.430 inch (1.09 centimeters) and outer legs each had a
height as viewed in FIG. 10 of about 0.250 inch (0.64 centimeter); a
desiccant impregnated polyurethane layer 160 had a height of about 0.125
inch (0.32 centimeter) and a width as viewed in FIG. 10 of about 0.416
inch (1.05 centimeters); a polyurethane secondary seal 155 had a width of
about 0.450 inch (1.143 centimeters) and a height of about 0.125 inch
(0.32 centimeter) as viewed in FIG. 10. The edge assembly RES-value of the
unit 150 constructed as above described using the ANSYS program was
calculated to be 79.1 hr-.degree.F/BTU per inch of perimeter.
Shown in FIG. 11 is the cross sectional view of another embodiment of a
spacer of the instant invention. Spacer 163 has a structurally resilient
core 164. The core in the practice of the invention may be non-metal and
is preferably a polymeric core e.g. fiberglass reinforced plastic U-shaped
member 164 having a thin film 165 of insulating gas impervious material.
For example when air, argon or krypton is used in the compartment, the
thin film 165 may be metal. The structure of the spacer as well as the gas
barrier film are chosen so that the unit will contain the fill gas for the
desired unit lifetime. A spacer according to FIG. 11 using argon as a fill
gas and employing polyvinylidene chloride as the barrier film, the
preferred thickness of the polyvinylidene chloride will be at least 5 mils
and more preferably it will be greater than 10 mils.
If a material other than polyvinylidene chloride is used as the barrier
film, the proper thickness to retain the fill gas for the desired unit
lifetime may be adjusted depending on the material's gas containment
characteristics.
The fill gas retention characteristics of the unit according to the instant
invention is measured by the above referred DIN 52293.
For argon, the film 165 may be a 0.0001 inch (0.000254 centimeter) thick
aluminum film or a 0,005 inch thick film of polyvinylidene chloride. As
used herein the argon impervious material has a permeability to argon of
less than 5%/yr. The invention contemplates having a core 164 and a thin
layer of film 165 or several layers 164 and 165 to build up a laminated
structure. Using the spacer 163 having the aluminum film in place of the
spacer 155 of the unit 150 in FIG. 10 the edge assembly RES-value for the
unit 150 of FIG. 10 is expected to be about 120. This is about a 50%
increase in the RES-value by changing the spacer to a thinly metal cladded
plastic spacer. Using the spacer 163 having a polyvinylidene chloride film
of a thickness of 0.005 inch, the edge assembly RES-value of the unit 150
of FIG. 10 is also expected to be about 120.
The instant invention also contemplates having a spacer 163 of FIG. 11
whose body is made entirely from a polymeric material having moisture/gas
impervious characteristics. Such a spacer body may be reinforced (e.g.
fiberglass reinforced) but would not include any film barrier (i.e. the
spacer 163 would not include a thin film 165). Such a polymeric material
would preferably be a halogenated polymeric material including
polyvinylidene chloride, polyvinylidene flouride, polyvinyl chloride or
polytrichlorofluoro ethylene. The edge assembly of such a spacer 163 made
entirely of a polymeric material would have a high edge assembly RES-value
expected to be comparable to the spacer of FIG. 11.
The spacer of the instant invention, in addition to acting as a barrier to
the insulating gas in the compartment 18, is structurally sound. As used
herein and in the claims "structurally sound" means the spacer maintains
the glass sheets in a spaced relationship while permitting local flexure
of the glass due to changes in barometric pressure, temperature and wind
load. The feature of maintaining the glass sheets in a fixed spacer
relationship means that the spacer prevents the glass sheets from
significantly moving toward one another when the edges of the unit are
secured in the glazing frame. As can be appreciated less force is applied
to the edges of residential units mounted in a wooden frame than to edges
of commercial units mounted by pressure glazing in metal curtainwall
systems. Permitting local flexure means the spacer allows rotation of the
marginal edge portions of the glass about its edge during loading of the
types described while restricting movement other than rotation i.e.
translation. The degree of structural soundness is related to type of
material and thickness. For example metal may be thin where plastic to
have the same structural soundness must be thicker or reinforced e.g. by
fiber glass.
Embodiments of the instant invention may be used to improve the performance
of the prior art units. For example replacing the spacer of the unit 10 of
FIG. 1 with a stainless steel spacer is expected to increase the edge
assembly RES-value from 4.65 to 18.2 hr-.degree.F/BTU per unit of
perimeter. If the metal thickness is changed from 0.025 inch (0.06
centimeter) to 0.005 inch (0.0127 centimeter) the edge assembly R-value of
the unit 10 of FIG. 1 using the ANSYS program goes from 4.65 to 96.1
hr-.degree.F/BTU per inch of perimeter. Replacing the aluminum strip of
the unit in FIG. 4 with a stainless steel strip increases the edge
assembly RES from 4.5 to 44.4 hr-.degree.F/BTU per unit of perimeter.
The unit 150 of the instant invention having the spacer assembly 152 shown
in FIG. 10 is expected to have an edge heat loss similar to that of line
140. The unit 150 of the instant invention having the spacer assembly 163
shown in FIG. 11 is expected to have an edge heat loss between line 130
and 140 but close to line 130. Although the edge assembly of the instant
invention has an edge assembly RES-value less than the RES-value for edge
assemblies having organic spacers of the type shown in FIG. 3, the edge
assembly of the instant invention has distinct advantages. More
particularly, the spacer is metal, gas and moisture impervious plastic,
metal cladded plastic core, metal cladded reinforced plastic core, gas
moisture impervious film cladded plastic core, gas moisture film cladded
reinforced plastic core and is therefore more structurally sound. The
diffusion path i.e. the length and thickness of the gas and moisture
impervious adhesive sealant material is longer in the unit of the instant
invention and therefore for the same type of material filling the
diffusion path, the longer, thinner diffusion path of the instant
invention reduces the rate of fill gas loss. The argon gas path is longer
because it is limited to the adhesive layers 154 (see FIG. 10) whereas in
organic spacers the diffusion path is through the entire width of the
spacer surface. In the unit of FIG. 3 a metal barrier is provided to
reduce argon loss. The metal film coated on the plastic or PVDC coated
plastic has a thickness in the range of about 0.001-0.003 inch
(0.00254-0.00762 centimeter) which is a short diffusion path. The instant
invention has a long diffusion path e.g. greater than about 0.003 inch
(0.00762 centimeter) and a thin diffusion path e.g. less than about 0.0125
inch (0.32 centimeter). The unit shown in FIG. 10 has a diffusion path
length of about 0.250 inch (0.64 centimeter) and a diffusion path
thickness of about 0.010 inch (0.254 centimeter). The path length can be
increased by increasing the height of the legs of the spacer and the path
thickness decreased by decreasing the spacing between the legs of the
spacer and adjacent glass sheet.
In actual tests a unit having an edge assembly of the instant invention and
a unit having the edge assembly shown in FIG. 3 had essentially identical
RES values. It is believed that the bead on the interior of the spacer may
have insulated the spacer from convection cooling by the gases in the
compartment.
As was discussed the teachings of the invention may be used to increase
edge assembly RES-value of a unit by using the spacer shown in FIG. 11.
Shaping a fiberglass reinforced plastic core 164 and then sputtering a
thin film 165 of aluminum or adhering in any convenient manner a
gas/moisture impervious film such as a PVDC film prevents the egress of
argon limiting the path essentially to the sealant or adhesive between the
spacer and glass as was discussed for the unit 150 of FIG. 10.
As can now be appreciated the unit of the instant invention provides an
edge assembly having a metal spacer, a metal coated plastic spacer or a
plastic spacer or a multi-layered plastic spacer that retain insulating
gas other than air, e.g. argon, has a relatively high edge assembly
RES-value or low U-value and has structural soundness.
The discussion will now be directed to the U-value of the frame of the
unit. The frame also conducts heat and in certain instances e.g. metal
frames conduct sufficiently more heat than the edge assembly of the unit
such that the edge heat loss through the frame overshadows any increase in
thermal resistance to heat loss provided at the edge of the unit. Wooden
frames, metal frames with thermal breaks or plastic frames have high
resistance to heat loss and the performance of the edge heat loss of the
unit would be more dominant.
The invention is not limited to units having two sheets but may be
practiced to make units having two or more sheets e.g. unit 250 shown in
FIG. 20.
The discussion will now be directed to a method of fabricating the glazing
unit of the instant invention. As will be appreciated the unit of the
instant invention may be fabricated in any manner; however, the
construction of the unit is discussed using selected ones of the edge
assembly components taught in U.S. patent application Ser. No. 07/578,697
filed Sep. 4, 1990, in the names of Stephen C. Misera and William R.
Siskos and entitled A SPACER AND SPACER FRAME FOR AN INSULATING GLAZING
UNIT AND METHOD OF MAKING SAME which teachings are hereby incorporated by
reference.
With reference to FIG. 12, there is shown an edge strip 169 having a
substrate 170 having the bead 160 of moisture pervious adhesive having the
desiccant 162 mixed therein. In the preferred practice of the invention
the substrate is made of a material, e.g. metal or composite of plastic as
previously described, that is moisture and gas impervious to maintain the
insulating gas in the compartment and prevent the ingress of moisture into
the compartment, and has structural integrity and resiliency to maintain
the glass sheets in spaced relation to one another and yet accommodates a
certain degree of thermal expansion and contraction which typically occurs
in the several component parts of the insulating glazing unit. In the
practice of the invention, the substrate was made of 304 stainless steel
having a thickness of about 0.007 inch (0.0178 centimeter) thick, a width
of about 0.625 inch (1.588 centimeters) and a length sufficient to make
spacer frame to be positioned between glass sheets e.g. a 24-inch (0.6
meter) square shaped unit. The bead 160 is a polyurethane having a
desiccant mixed therein. A bead about 1/8 inch (0.32 centimeter) high and
about 3/8 inch (0.96 centimeter) wide is applied to the center of the
substrate 170 in any convenient manner.
As can be appreciated the desiccant bead may be any type of adhesive or
polymeric material that is moisture pervious and can be mixed with a
desiccant. In this manner the desiccant can be contained in the adhesive
or polymer material and secured to the substrate while having
communication to the compartment. Types of materials that are recommended,
but the invention is not limited thereto, are polyurethanes and silicones.
Further the bead may be the spacer dehydrator element taught in U.S. Pat.
No. 3,919,023 which teachings are hereby incorporated by reference.
Further, as can now be appreciated one or both sides of one or more sheets
may have an environmental coating such as the one taught in U.S. Pat. Nos.
4,610,771; 4,806,220; 4,853,256; 4,170,460; 4,239,816 and 4,719,127 which
patents are hereby incorporated by reference.
In the practice of the invention the metal substrate after forming into
spacer stock and the bead has sufficient structural strength and
resiliency to keep the sheets spaced apart and yet accommodates a certain
degree of thermal expansion and contraction which typically occurs in the
several component parts of the insulating glazing unit. In one embodiment
of the invention the spacer is more structurally stable than the bead i.e.
the spacer is sufficiently structurally stable or dimensionally stable to
maintain the sheets spaced from one another whereas the bead cannot. In
another embodiment of the invention both the spacer and the bead can. For
example, the bead may be a desiccant in a preferred spacer taught in U.S.
Pat. No. 3,919,023 to Bowser. As can be appreciated by those skilled in
the art, a metal spacer can be fabricated through a series of bends and
shaped to withstand various compressive forces. The invention relating to
the bead 160 carried on the substrate 170 is defined by shaping the
substrate 170 into a single walled U-shaped spacer stock with the
resultant U-shaped spacer stock being capable of withstanding values of
compressive force to maintain the sheets apart regardless of the
structural stability of the bead. As can be appreciated by those skilled
in the art the measure and value of compressive forces and structural
stability varies depending on the use of the unit. For example if the unit
is secured in position by clamping the edges of the unit such as in
curtainwall systems, the spacer has to have sufficient strength to
maintain the glass sheet apart while under compressive forces of the
clamping action. When the use is mounted in a rabbit of a wooden frame and
caulking applied to seal the unit in place, the spacer does need as much
structural stability to maintain the glass sheets apart as does a spacer
of a unit that is clamped in position.
The edges of the strip 150 are bent in any convenient manner to form outer
legs 156 of a spacer 158 shown in FIG. 10. For example the strip 170 may
be pressed between bottom and top rollers as illustrated in FIGS. 13-16.
With reference to FIG. 13 the strip is advanced from left to right between
roll forming stations 180 thru 185. As will be appreciated by those
skilled in the art, the invention is not limited to the number of roll
forming stations or the number of roll forming wheels at the stations. In
FIG. 14 the roll forming station 180 includes a bottom wheel 190 having a
peripheral groove 192 and an upper wheel 194 having a peripheral groove
196 sufficient to accommodate the layer 160. The groove 192 is sized to
start the bending of the strip 170 to a U-shaped spacer and is less
pronounced than groove 198 of the bottom wheel 200 of the pressing station
181 shown in FIG. 15 and the remaining bottom wheels of the downstream
pressing station 182 thru 185.
With reference to FIG. 16, the lower wheel 202 of the roll forming station
185 has a peripheral groove 202 that is substantially U-shaped. The spacer
stock exiting the roll forming station 185 is the U-shaped spacer 158
shown in FIG. 10.
As can now be appreciated the grooves of the upper roll forming wheels may
be shaped to shape the bead of material on the substrate.
In the practice of the invention the bead 160 was applied after the spacer
stock was formed e.g. the substrate formed into a U-shaped spacer stock.
This was accomplished by pulling the substrate through a die of the type
known in the art to form a flat strip into a U-shaped strip.
As can be appreciated, everything else being equal, loose desiccant is a
better thermal insulation than desiccant in a moisture pervious material.
However, handling and containing loose desiccant in a spacer in certain
instances is more of a limitation than handling desiccant in a moisture
pervious matrix. Further having the desiccant in a moisture pervious
matrix increases the shelf life because the desiccant takes a longer
period of time to become saturated when in a moisture and/or gas pervious
material as compared to being directly exposed to moisture. The length of
time depends on the porosity of the material. However, the invention
contemplates both the use of loose desiccant and desiccant in a moisture
pervious matrix.
The spacer stock 158 may be formed into a spacer frame for positioning
between the sheets. As can be appreciated, the layers 154 and 155, shown
in FIG. 10 may be applied to the spacer stock or the spacer frame. The
invention is not limited to the materials used for the layers 154 and 155;
however, it is recommended that the layers 154 provide high resistance to
the flow of insulating gas in the compartment 18 between the spacer 152
and the sheets 12 and 14. The layer 155 may be of the same material as
layers 154 or a structural type adhesive e.g. silicone. Before or after
the layers 154 and/or 155 are applied to the spacer stock, a piece of the
spacer stock is cut and bent to form the spacer frame. Three corners may
be formed i.e. continuous corners and the fourth corner welded or sealed
using a moisture and/or gas impervious sealant. Continuous corners of
spacer frame incorporating features of the invention are shown in FIGS. 17
and 19. However, as can be appreciated, spacer frames may be formed by
joining sections of the spacer stock and sealing the edges with a moisture
and/or gas impervious sealant or welding the corners together.
With reference to FIG. 18 a length of the spacer stock having the bead is
cut and a notch 207 and creases 208 are provided in the spacer stock in
any convenient manner at the expected bend lines. The area between the
creases is depressed e.g. portion 212 of the outer legs 156 at the notch
are bent inwardly while the portions on each side of the crease are biased
toward each other to provide a continuous overlying corner 224 as shown in
FIG. 17. The non-continuous corner e.g. the fourth corner of a rectangular
frame may be sealed with a moisture and/or gas impervious material or
welded. As can be appreciated the bead at the corner may be removed before
forming the continuous corners.
With reference to FIG. 19, in the practice of the invention spacer frame
240 was formed from a U-shaped spacer stock. A continuous corner 242 was
formed by depressing the outer legs of the spacer stock toward one another
while bending portions of the spacer stock about the depression to form a
corner e.g. 90.degree. angle. As the portions of the spacer stock are bent
the depressed portions 244 of the outer legs move inwardly toward one
another. After spacer frame was formed, layers of the sealant were
provided on the outer surface of the legs 18 of the spacer frame and the
bead 26 on the inner surface of the middle leg of the spacer frame. The
unit 10 was assembled by positioning and adhering the glass sheets to the
spacer frame by the sealant layers 154 in any convenient manner.
A layer 155 of an adhesive if not previously provided on the frame is
provided in the peripheral channel of the unit (see FIG. 10) or on the
periphery of the unit. Argon gas is moved into the compartment 18 in any
convenient manner to provide an insulating unit having a low thermal
conducting edge.
As can be appreciated by those skilled in the art, the invention is not
limited by the above discussion which was presented for illustrative
purposes only.
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